Power sensor for a current carrying conductor

ABSTRACT

A power sensor is disclosed for a current carrying conductor. In at least one embodiment, the sensor includes at least one ferromagnetic core, a secondary winding, and at least one of connecting elements for a load or a load. The secondary winding is designed as an injection molded part on an insulating layer that is injection molded onto the ferromagnetic core.

PRIORITY STATEMENT

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/EP2007/007493 which has anInternational filing date of Aug. 27, 2007, which designates the UnitedStates of America, the entire contents of each of which are herebyincorporated herein by reference.

FIELD

At least one embodiment of the present application is generally directedto a power sensor.

BACKGROUND

For the monitoring of currents and voltages in power technology, due totheir high values these must generally be converted into proportionalcomparison values by means of an intermediary unit, in order to be ableto record and analyze them with conventional measuring devices.

In switchgear and switching device technology so-called currentconverters are known, which in the “plug-in current transformer” formatsurround a current-carrying conductor in an annular manner and are thusalso designated as donut-type current transformers. In accordance withtheir electromagnetic functional principle, these converters are alsodesignated as a special type of transformer.

Around a core of ferromagnetic material, which surrounds a primarywinding comprising the conductor with the current to be determined, runsa secondary winding, to the ends of which is connected a resistance—theso-called load—at which in turn a voltage value proportional to theprimary current can be measured.

This value is, for example, processed in electrically monitoredcircuit-breakers in relation to overload protection for the connectedconsumers.

SUMMARY

The known donut-type current transformers are however relativelyexpensive to produce and assemble. Thus, at least one embodiment of thepresent application is directed to a power sensor which is simpler or asthe case may be cheaper to manufacture.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are explained in the following withreference to the examples represented in the attached drawings, inwhich;

FIG. 1 shows the structure of a half-shell;

FIG. 2 shows the structure of a power sensor made up of two half-shells;

FIG. 3 shows the power sensor around a current-carrying conductor with asmall current;

FIG. 4 shows the power sensor around a current-carrying conductor with alarge current; and

FIG. 5 shows the possible structure of the load.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

FIG. 1 shows the structure of a half-shell 11. The annular or pipe-likehalf-shell is manufactured using multi-component injection moldingmethods and contains the ferromagnetic core 12, the secondary winding 13and one or two connecting elements 14 for a load.

The ferromagnetic core 12 is laid in the injection molding tool as amolded part or is made of thermoplastic material filled with magneticpowder, and is likewise suitable for injection molding.

After in the course of the subsequent injection molding procedure thecore half-shell 11 has been enveloped with an insulating layer 15, whichhas a suitable external contour according to the desired winding, thesecondary winding 13 from electrically conductive plastic can now beapplied, whereby in this step corresponding connecting elements 14 andconnecting elements 16 for the half-shells 11, 21 can if appropriate beintegrated as metal parts. Finally an outer sleeve 18 is applied in afurther injection molding procedure.

FIG. 2 shows the construction of a power sensor 20 from two half-shells11 and 21. The parts identified with reference numbers 11, 12, 13, 14,15 and 18 correspond to the parts with reference numbers 21, 22, 23, 24,25 and 28. The half-shell 21 can be identical to the half-shell 11, orthe studs 16 can be replaced by a notch 27.

As is evident from FIG. 2, the half-shells 11 and 21 can also beconnected with an elastic hinge 29, in particular a foil hinge, and canthus be manufactured in one piece. The winding 13 or 23 respectively canif appropriate run across the hinge 29.

In one embodiment of the invention, the load is embodied as a conductiveplastic string in one piece with the winding 13, 23. As a result of thecharacteristic of conductive plastics, of increasing their volume in thecase of a flowing current, further options such as for example thedirect actuation of a mechanical device are opened up. This can be atrigger for cutoff purposes or other mechanical actuator.

For the realization of mechanical movements, part of the transformer isexpediently embodied as shown in FIGS. 3 and 4 in the manner of a“bi-metal” 31, 32, in order to enable the execution of a relativelylarge mechanical movement with a minor change in volume of the area 32containing the load, which is in turn suitable for the release of apre-tensioned mechanism according to the “mousetrap principle”, forexample for an overload cutoff. FIG. 3 represents the circumstances inthe case of rated voltage (I¹), FIG. 4 in the case of overcurrent (I2,where I2>I1). In FIG. 4 the position of the area 32 containing the loadin the case of rated voltage (I¹) is indicated by a broken line. Themovement of the area 32 containing the load is indicated by Δ.

It is here advantageous to embody the load 51 in a meander-like form asshown in FIG. 5, in order both to realize an appropriate resistancevalue and to convert the increase in volume of the conductive plastic inthe deflection path in a particularly effective manner.

With the inventive combination of multi-component injection moldingtechnology as described and the use of conductive plastics, amultiplicity of advantages of a technical and economic nature arise.

The use of injection molding to form the unit opens up possibilities forcost-effective, readily-automated production especially through theincorporation of mechanical components into an integrated design of thecomplete product.

Example embodiments being thus described, it will be obvious that thesame may be varied in many ways. Such variations are not to be regardedas a departure from the spirit and scope of the present invention, andall such modifications as would be obvious to one skilled in the art areintended to be included within the scope of the following claims.

The invention claimed is:
 1. A power sensor for a current-carryingconductor, comprising: at least two ferromagnetic cores; a secondarywinding including a first and second portion, each portion embodied asan injection molded part on an insulating layer injection molded onto arespective one of the at least two ferromagnetic cores; two half-shells,each including at least one of the at least two ferromagnetic cores andeither the first or the second portion of the secondary winding, theportions of the secondary winding of the two half-shells beingphysically connected via a connecting part embodied as an injectionmolded part.
 2. The power sensor as claimed in claim 1, furthercomprising an insulating layer embodied as an injection molded part as acover for the secondary winding.
 3. The power sensor as claimed in claim2, wherein the two half-shells are electrically connected to each othervia a connecting part embodied as an injection molded part.
 4. The powersensor as claimed in claim 3, wherein the connecting part is embodied asa film hinge.
 5. The power sensor as claimed in claim 1, wherein the twohalf-shells are electrically connected to each other via a connectingpart embodied as an injection molded part.
 6. The power sensor asclaimed in claim 5, wherein the connecting part is embodied as a filmhinge.
 7. The power sensor as claimed in claim 1, wherein the connectingpart is embodied as a film hinge.
 8. The power sensor as claimed inclaim 1, wherein the at least two ferromagnetic cores are embodied as amolded part.
 9. The power sensor as claimed in claim 1, wherein the atleast two ferromagnetic cores are embodied as an injection molded part.10. The power sensor as claimed in claim 9, wherein the at least twoferromagnetic cores are embodied as an injection molded part inthermoplastic material filled with magnetic powder.
 11. The power sensoras claimed in claim 1, further comprising: at least one of integratedconnecting elements and connecting elements for the half-shells.
 12. Thepower sensor as claimed in claim 1, wherein the load is embodied as aconductive plastic string.
 13. The power sensor as claimed in claim 1,further comprising at least one of a load and connecting elements forthe load.
 14. The power sensor as claimed in claim 1, wherein theconnecting part includes a segment of the secondary winding.
 15. A powersensor for a current-carrying conductor, comprising: at least oneferromagnetic core; a secondary winding embodied as an injection moldedpart on an insulating layer injection molded onto the at least oneferromagnetic core; and at least one of a load and connecting elementsfor the load, wherein the load is embodied as a conductive plasticstring, at least one area which contains or surrounds the load, whereinthe power sensor is embodied to move the at least one area by way of acurrent-dependent change in volume of an electrically conductive part ofthe sensor.
 16. The power sensor as claimed in claim 15, where themovement is embodied to release a pre-tensioned mechanism.
 17. The powersensor as claimed in claim 15, wherein the power sensor furthercomprises two half-shells, each including at least one ferromagneticcore.